Evaluation of the J2000 groundwater component

1 Decision for z-score normalization

Since the z-score normalization is used for the evaluation of the Explore2 project, it makes sense to use it here as well for reasons of comparability. To unify it the data was monthly aggregated before the normalization. The normalized value is called Standardized Piezometric Level Index (SPLI) in the Explore2 report, which nomenclature will be used from now on. Also the begin of the comparison was set to the year 2004, so there is the most data for all stations available and the simulation time is reduced.

Figure 1: Time series of SPLI

For the aggregation to average monthly values, hydrological years with less than 90% data availability were removed.

Figure 2: Regime of hydrological year

Figure 3: Duration curves

Figure 4: NSE(SPLI) of J2K output to ADES

2 Limitations due to the calibration

If you take a look at the plots, two unwanted patterns are recognizable:

• High frequency in time series, resulting in 95th-Percentile = maximum in duration curves \(\rightarrow\) RG1_max is too small
• No variation in time series and values around zero (the mean), resulting in IQR = 0 \(\rightarrow\) RG1_k is too big

These two criteria give the possibility to evaluate/improve the groundwater component of HRUs with no piezometers in them.

3 Evaluation criteria

For further analysis and the calibration of the model to improve the representation of the groundwater component multiple goodness-of-fit tests will be used. Since the main purpose of the model is to simulate the discharge in the Loire catchment, the Kling-Gupta efficiency (KGE) of the square root of the discharge, will be the criterion (also used in Explore2 for J2K model). For the groundwater component two different types of criteria will be used:

• if there are reference piezometers: the Nash-Sutcliffe efficiency of the SPLI, Correlation, time lag of maximum/minimum of the regime
  
• if there are no reference piezometers: difference of 95th-Percentile to maximum and IQR

4 Identifying range of RG1_max and RG1_k for calibration

Table 1: Cailbration parameters to identify calibration range

Run	RG1_max	RG1_k
1	10	10
2	10	30
3	10	180
4	10	360
5	10	500
6	50	10
7	50	30
8	50	180
9	50	360
10	50	500
11	100	10
12	100	30
13	100	180
14	100	360
15	100	500
16	500	10
17	500	30
18	500	180
19	500	360
20	500	500
21	1000	10
22	1000	30
23	1000	180
24	1000	360
25	1000	500

Figure 5: IQR and difference between maximum and 95th-percentile (max_perc) for each hgeoID